After players completed a new release, they could sell it back to the company for a fraction of the MSRP, which GameStop would then turn around and sell to a new player for almost the full cost of the new version of the game
The first Warlock is a 4/4 for five mana with deathtouch that says when you gain life, at the end of your turn can force your foes to sacrifice dorks and then Raise Dead
This means you can play it earlier on if needed, which can be important for quicker games or formats
Second, it allows you to hit important power/toughness breakpoints in creature mirrors
It is very expensive though
Tyranitar and Carnivine's abilities make their attacks do more damage, Magnezone and Raichu's cause them to take less damage, and Heatran and Rotom's removes their retreat cost